BSD is correct. The earliest "glass cockpit", a NASA-FAA Boeing 737 TCV (Terminal Configured Vehicle) was equipped with flexible workstations of enhanced instrumentation based on the Boeing 2707 SST.
Well Duh! I did see that cockpit, feel rather foolish now. But I couldn't get the external cockpit on the NASA Convair 580 out of my mind and knew that was not it.
Good find.